I have a provider-hosted SharePoint Online add-in project. In this project I have added a lookup field with name CaseLawyer and deployed the app in the site. After that, I have deleted this field form the list and added a new lookup field with name AuthorizedTo and upgraded my app. Now when I open the list view I still see the old field (CaseLawyer) and don't see the new field (AuthorizedTo).
Expand your "Case" list item in the solution explorer and edit the "Schema.xml" file in order to remove all reference to the field you want to delete.
I once have similar problem with a field i have renamed and it didn't work with the list designer but succeed on editing directly the schema.